“Let It Go,” the new single from Dragonette, came out just in time for spring. You want feel-good music? This is it. It has the gleam of a Robyn track, only without the Scandinavian angst. It’s glittery, sunshiny electro pop—the kind of song that can make you skip down the street imaging yourself in some big music-video dance number. The band’s third album is due later this year, and if “Let It Go” is any indication, it will be well worth the wait.